The present invention relates to a plastic sorting device by which plastic pieces resulting from recycling are sorted according to kind.
In recent years, recycling of waste refuse has advanced rapidly. In this connection, as a technique for sorting crushed plastic pieces, there is a plastic sorting device as shown in FIG. 6. This plastic sorting device comprises a frictional charging device 3 that is disposed below a hopper 2 adapted to have a plurality of kinds of plastic pieces 1 put therein and that is used to charge the plastic pieces 1 to give the latter a polarity and an amount of electric charge according to kind, and an electrostatic separator G disposed below said frictional charging device 3 and used to separate the charged plastic pieces 1 according to polarity and amount of electric charge.
And the electrostatic separator G comprises a metal drum electrode 5 disposed below the chute 3b of the frictional charging device 3, a high voltage electrode 6 disposed obliquely above the metal drum electrode 5, and a brush 10 for scraping the plastic pieces 1 sticking to the peripheral surface of the metal drum electrode 5. In addition, said metal drum electrode 5 is constructed for rotation around a horizontal axis 5a in a predetermined direction and is grounded. Connected to the high voltage electrode 6 is, for example, the cathode of a high voltage power source device 7, the anode thereof being grounded? This connection provides a sorting electrostatic field formed between the high voltage electrode 6 and the metal drum electrode 5.
First and second separating vessels 8 and 9 for collecting according to kind the plastic pieces 1 that have passed through. this sorting electrostatic field are fixedly disposed below the metal drum electrode 5.
In said plastic sorting device, when the plastic pieces 1 are put in the hopper 2, they are fed from the hopper 2 into the frictional charging device 3, where they are stirred and each frictionally charged to have a predetermined polarity and an amount of electric charge according to kind-based electrification rank. Thereafter, they fall down to the electrostatic separator G, pass through the sorting electrostatic field, and are collected in the separate vessels 8 and 9 as they are classified according to polarity and amount of electric charge.
In this connection, in said plastic sorting device, the plastic pieces 1 are each frictionally charged in the frictional charging device 3 to have a polarity and an amount of electric charge, with an electrification rank corresponding to the plastic pieces 1 established, and are separated by the electrostatic separator G and collected in the vessels 8 and 9 according to kind.
However, the crushed plastic pieces 1 put in the hopper 2 differ in size (weight), so that when the plastic pieces 1 charged in the frictional charging device 3 pass through the sorting electrostatic field, their collected positions may vary according to the size of the plastic pieces 1 even if they assume the same position in the electrification rank, making it impossible to attain correct electrostatic separation according to kind.
Accordingly, the present invention has for its object the provision of a plastic sorting device capable of solving said problem.
The means for solving the problem according to the invention is to provide an arrangement comprising a frictional charging device for stirring and frictionally charging different kinds of crushed plastic pieces, a pair of electrostatic separating sections disposed below said frictional charging device for electrostatic separation of each plastic piece according to its polarity and amount of electric charge, each of said electrostatic separating sections having a drum electrode rotatable around a predetermined horizontal shaft, and an opposed electrode disposed adjacent said drum electrode through a separating space serving as a sorting electrostatic field, characterized by further comprising: a collecting section that is common to the electrostatic separating sections and that is disposed below the separating space between said drum electrodes for separately collecting plastic pieces that have passed through said separating space and thereby been separated, said collecting section having a plurality of collecting chambers for collecting plastic pieces according to kind; and a classifying section that, in frictionally charging said different kinds of crushed plastic pieces by the frictional charging device, classifies the plastic pieces according to size and load them into the frictional charging device.
In the above arrangement, plastic pieces are classified according to size in the classifying section and then loaded into the frictional charging device, where they are stirred, and each plastic piece is electrostatically separated according to its polarity and amount of electric charge in the pair of electrostatic separating sections disposed below said frictional charging device. In these electrostatic separating sections, the drum electrode rotatable around a predetermined horizontal shaft is rotated, the opposed electrode is disposed adjacent said drum electrode through a separating space serving as a sorting electrostatic field and has a voltage imposed thereon, and the plastic pieces are passed through the separating space and are separately collected in the common collecting section.
Further, the collecting section has partition walls for partitioning said plurality of collecting chambers, said partition walls being constructed to be adjustable for horizontal movement toward and away from the drum electrode, and a moving means is provided for horizontally moving the partition walls to the fall positions corresponding to the size of each plastic piece.
According to this arrangement, on the basis of the size of each plastic piece, the moving means is used for adjustment so as to horizontally move the partition walls toward and away from the drum electrode, so that electrostatic separation of the plastic pieces is correctly effected.
Further, the collecting section has partition walls for partitioning said plurality of collecting chambers, said partition walls being constructed to be swingable around support shafts parallel to the horizontal shaft of the drum electrode, and a swing means is provided for swinging the partition walls around the support shafts to the fall positions corresponding to the size of each plastic piece.
According to this arrangement, on the basis of the size of each plastic piece, the swing means is used to swing the partition walls around the support shafts parallel to the horizontal shaft of the drum electrode, so that electrostatic separation of the plastic pieces is correctly effected.